Anthropoids consist of New World
Monkeys and Catarrhini (Old World Monkeys & Apes)

One of the
superfamilies within Catarrhini, Hominoidae includes family Hominidae
(Australopithecines & Homo) and Pongidae (Chimpanzee & Gorilla).
Sometimes Pongidae is included in Hominidae in which case subfamily Homininae
is used for Homo. Modern humans and great apes are descendants of a common
ancestor, which lived about 5 million years ago. [In other words, humans did
not descend from apes. Hominoids diverged from monkeys 25 mya. Gibbons and
orangutans diverged from other apes 10 and 8 mya, respectively.

Hypotheses on
the emergence of modern humans:

1.
Multiregional evolution model: Proposes an evolutionary trend throughout the
old world towards modern Homo sapiens, with little population migration and no
population replacement. It emphasizes regional continuity in the evolution from
H.erectus to archaic H.sapiens, and later to anatomically modern humans. The
strongest piece of evidence for this hypothesis is that distinctive
characteristics found today in different geographical regions are also found in
H.erectus populations of the same region.

2. Out of
Africa model: Evolution of Homo sapiens in one place only (east Africa),
followed by extensive population migration across the old world resulting in
the replacement of existing premodern population (Homo erectus). Smaller
interpopulation genetic divergence than intrapopulation divergence supports this
hypothesis. The greater genetic diversity among sub-Saharan African populations
may indicate a longer period of separation of populations within Africa than
elsewhere. Pairs of African populations are some 50% more genetically distinct
from each other than are any other pairs of populations. Not only for mtDNA,
but also for many nuclear loci and some regions of Y-chromosome DNA, Africans
have higher diversity. This would imply a much longer population history for
Africa. The initial mtDNA split was found between Africans and others, followed
by progressively younger calibrated ages for specific Asian, Australian, New
Guinea, and European mtDNA types. In summary, both mtDNA and Y-chromosome
studies (as well as other nuclear DNA studies) indicate a recent African origin
for modern humans, probably within the last 200,000 years. The oldest
anatomically modern human fossils (over 100,000 years old) are found in Africa
supporting the Out of Africa model as well. The latest one of those is the
recent finding (Homo sapiens idÓltu) in Herto, Ethiopia which has been dated
approximately 160.000 yr old (White
et al, 2003; Clark
et al, 2003; New Scientist
Commentary; Science
News Commentary).

4. Origin of modern humans (modern Homo sapiens:
humans with a flair of technology and innovation; use of language; a capacity
for artistic expression; an introspective consciousness; a sense of morality;
domestication of animals and plants) about 200 thousand years ago.

Other trends: disappearance of sexual dimorphism
in the last million years, less projecting face, more prominent nose and chin,
lighter skeleton, smaller brow-ridges.

Time table of speciation towards the Homo lineage

Homo sapiens sapiens occurred around 200,000
years ago

The transition from H.erectus to H.sapiens
happened about 500,000 years ago

H.erectus emerged in Africa more than 1.7 million
years ago

Bipedal Australopithecines appeared (5 mya)

The Homininae lineage (subfamily) diverged from
Chimpanzee lineage 5-7 million years ago

2. Jaw and teeth size and shape (smaller, less
projected jaws with small teeth and non-projected canines together with smaller
face)

3. Mechanisms of locomotion (bipedal walking and
running)

Australopithecus
(Southern ape): The earliest Hominines lived in eastern and southern Africa about
5 to 1 mya (now extinct). They developed from Kenyapithecine and
pre-Australopithecines. They are the transitional species between apes and
humans. The adoption of bipedal locomotion may have been the motive for
splitting from the ape lineage. In some ways they were similar to living apes
in having small brains (450 - 550 cc) and ape-like body proportions. However,
they were distinguished from them by their upright posture and bipedal
(two-footed) gait. In addition, the teeth of Australopithecines included
smaller canines as well as thickened enamel on the molars. These features are
also found in humans. Their height was 1 - 1.5m. It comprised both gracile
(ramidus, afarensis, africanus) and robust (aethiopicus, robostus, boisei)
forms. The earliest well-known fossil in the homininae lineage is A.afarensis
which is the ancestor of both Homo lineage and other Australopithecines [Lucy
'AL 288-1' found in Ethiopia in 1974 is a 40% complete fossil of A. afarensis
from 3.6 - 3.8 mya; A. ramidus found in Aramis/Ethiopia in 1994 is from 4.4 mya
and is the missing link between the common ancestor (of apes and Homo) and
human family trees, and closer to chimpanzee]. A.africanus appeared about 3 mya
[Taung baby (2.8 million years old) found in South Africa in 1924]. Contrary to
the original idea, it may not have evolved from afarensis (see Berger Lee: Nat
Geog 1998; 194(2):90) but afarensis and africanus may be sister species that
share a missing-link ancestor. A.africanus is closer to H.habilis than the
other Australopithecus species. Surprisingly, africanus has longer arms and
shorter legs (more ape-like) than the earlier afarensis. They also have larger
brain than afarensis and their skull features resemble those of the first Homo
species. No tools were found with Australopithecine fossils. Whether the genus Homo
split off before or after the early robust Australopithecine line is not known
but Homo co-existed with robust Australopithecines. The evolutionary transition
to Homo probably occurred between about 2.3 to 2.7 million years ago.

Homo habilis (skilful person): The
first species of our own genus Homo appeared in East Africa around 2.5 mya.
Developed from gracile Australopithecus (africanus). They had a larger brain
capacity (650 - 800 cc) than Australopithecus. [ER-1470 = H.habilis, older than
2 mya]. Some H.habilis fossils are associated with tools. The oldest stone
tools are about 2.5 million years old and were found associated with the
fossils of H.habilis.

Homo erectus: Appeared in East Africa
1.7 mya or earlier, eventually inhabited the Old World. By about 1.5 million
years ago, descendant forms of H.erectus are known from the tropical areas of
the Old World. They spread out of Africa and tropicals 1.0 to 0.7 mya (the
African population continued to evolve and gave rise to modern humans). They
were hunter-gatherers with a cranial capacity of 775-1250 cc. [Peking man =
H.erectus pekinensis; Turkana boy found in Tanzania = H.erectus, also found in
Java, India and Europe]. One descent line from H.erectus led to the
Neanderthals. H.erectus may have survived in parts of Asia long after it had
become extinct (or evolved into a new species) elsewhere. A number of H.erectus
fossils from two sites in Java were dated to only 30 to 50 thousand years ago.

Homo
heidelbergensis: By about 600,000 years ago, some H.erectus populations in Africa,
and probably also in Europe, had changed sufficiently to be recognized as a new
species. The first fossil belonging to this species was found near Heidelberg
and dated to 500,000 years ago. A large brain size, a less projecting face, a
more prominent nose and a more inflated braincase are typical of
H.heidelbergensis. It is believed that H.heidelbergensis split into
H.neanderthalis and H.sapiens. The common ancestor to Neanderthal and modern
humans was dated between 550 and 690 thousand years.

Homo sapiens
neanderthalensis: An archaic subspecies (300 - 35 thousand years ago= Mid-late
Palaeolithic) lived in Europe and parts of Asia. The first Neanderthal skull
was found in the Neander valley in 1857. Since then more fossils have also been
found in Spain and Israel. Variation observed between the Neanderthal and human
species is much greater than that observed between the human lineages
themselves, but not as great as that between the chimpanzee and human lineages.
This supports the idea that Neanderthals went extinct without contributing
mtDNA to modern humans and were a distinct species (i.e., interbreeding between
Neanderthals and H.sapiens sapiens did not occur). The physical characteristics
of Neanderthals are heavy brow ridges, elongated skull and long jaw. They
probably had a larger brain than modern humans. They looked after their
disabled and buried their dead ritualistically. Recent evidence suggests their
physical capacity for the sounds of speech.

Homo sapiens (intelligent person): The
final evolutionary form of humans developed from Homo erectus. In Africa, the
species H.habilis, H.erectus and H.sapiens were probably a continuum of
chronospecies. These repeatedly expanded out of Africa and replaced the
previous colonizers of the Eurasian land mass. The brain size is 1400 cc on
average, frontal lobes are developed, face projection is decreased, the size of
teeth is decreased and a chin is appeared. Homo sapiens sapiens is another
separate lineage which goes back more than 100 thousand years ago. Originated
in Africa and replaced the Neanderthals. The Cro-Magnon people from
35 - 40 thousand years ago are believed to be prehistoric H.sapiens sapiens who
are the ancestors of Europeans. They developed aesthetic feelings and are
associated with Upper Palaeolithic culture. All current human races are the
same species. There are larger differences between individuals within any
racial groups than there are between the averages of each race.

According to molecular studies, our closest
relatives are the chimpanzee and the pigmy chimpanzee (bonobo). Our next
nearest relative is the gorilla. Cladograms based on craniodental
characteristics, however, place humans and orangutans in the same clade and
gorilla and chimpanzees in another (see Collard & Wood, 2000
and Pilbeam, 1996 for
details and the conclusion that hominoid dental characters are not reliable for
phylogenetic reconstruction).

Primates consist of four groups

1. Prosimians (including lemur): First group
evolved from shrew-like mammals about 70 mya.

2. New world monkeys: Marmoset, howler and spider
monkey.

3. Old world monkeys (baboons and macaques): From
which hominoids split off.